n. 冲积层, 淤积层

[机] 冲积层

[ noun ]
clay or silt or gravel carried by rushing streams and deposited where the stream slows down
<noun.object>

Alluvium \Al*lu"vi*um\, n.; pl. E. {Alluviums}, L. {Alluvia}.
[L., neut. of alluvius. See {Alluvious}.] (Geol.)
Deposits of earth, sand, gravel, and other transported
matter, made by rivers, floods, or other causes, upon land
not permanently submerged beneath the waters of lakes or
seas. --Lyell.